Rubber compositions containing bis anil compounds

ABSTRACT

The present invention relates to rubber compositions containing an elastomer containing olefinic unsaturation and a bis anil compound of the formula ##STR1## where R 1  and R 2  may be the same or different and are independently selected from alkyls having from 1 to 5 carbon atoms and X is selected from the group consisting of H; OH; OAlk where Alk is an alkyl having from 1 to 3 carbon atoms; COOH and; COO -  M +  where M is a metal selected from the group consisting of Zn, Na, Ca and Mg; and y is 0 to 2.

FIELD OF THE INVENTION

The present invention relates to the use of bis anil compounds in rubbercompositions.

BACKGROUND OF THE INVENTION

Over the years, rubber compounders have used various materials in rubberto obtain the desired processing characteristics, ultimate properties ofthe finished product or cost control. Such materials may be classifiedas vulcanizing agents, accelerators, accelerator activators andretarders, age resistors, processing aids, reinforcing pigments andresins, inert fillers and special purpose materials. With theever-present demands to improve the processing characteristics,properties and costs, rubber compounds are forever on the lookout fornew materials for use in rubber.

U.S. Pat. No. 3,446,861 discloses a catalyst for the selectivecyclodimerization of 1,3-butadiene. The catalyst comprises (1) ironsalts or iron complexes, (2) an organometallic reducing agent and (3)certain ligands containing nitrogen. Representative of such ligandsinclude biacetyl-bis-anil, biacetyl-bis-(4-hydroxyanil) andbiacetyl-bis-(4-ethoxyanil).

Quite surprisingly, it has been discovered that use of bis anilcompounds improve properties of rubber when added.

SUMMARY OF THE INVENTION

The present invention relates to the use of bis anil compounds in rubbercompositions.

DETAILED DESCRIPTION OF THE INVENTION

There is disclosed a rubber composition comprising an elastomercontaining olefinic unsaturation and a bis anil compound of the formula##STR2## where R¹ and R² may be the same or different and areindependently selected from alkyls having from 1 to 5 carbon atoms and Xis selected from the group consisting of H; OH; OAlk where Alk is analkyl having from 1 to 3 carbon atoms; COOH and; COO⁻ M⁺ where M is ametal selected from the group consisting of Zn, Na, Ca and Mg; and y is0 to 2.

The present invention may be used to process sulfur vulcanizable rubbersor elastomers containing olefinic unsaturation. The phrase "rubber orelastomer containing olefinic unsaturation" is intended to include bothnatural rubber and its various raw and reclaim forms as well as varioussynthetic rubbers. In the description of this invention, the terms"rubber" and "elastomer" may be used interchangeably, unless otherwiseprescribed. The terms "rubber composition," "compounded rubber" and"rubber compound" are used interchangeably to refer to rubber which hasbeen blended or mixed with various ingredients and materials and suchterms are well known to those having skill in the rubber mixing orrubber compounding art. Representative synthetic polymers are thehomopolymerization products of butadiene and its homologues andderivatives, for example, methylbutadiene, dimethylbutadiene andpentadiene as well as copolymers such as those formed from butadiene orits homologues or derivatives with other unsaturated monomers. Among thelatter are acetylenes, for example, vinyl acetylene; olefins, forexample, isobutylene, which copolymerizes with isoprene to form butylrubber; vinyl compounds, for example, acrylic acid, acrylonitrile (whichpolymerize with butadiene to form NBR), methacrylic acid and styrene,the latter compound polymerizing with butadiene to form SBR, as well asvinyl esters and various unsaturated aldehydes, ketones and ethers,e.g., acrolein, methyl isopropenyl ketone and vinylethyl ether. Specificexamples of synthetic rubbers include neoprene (polychloroprene),polybutadiene (including cis-1,4-polybutadiene), polyisoprene (includingcis-1,4-polyisoprene), butyl rubber, styrene/isoprene/butadiene rubber,copolymers of 1,3-butadiene or isoprene with monomers such as styrene,acrylonitrile and methyl methacrylate, as well as ethylene/propyleneterpolymers, also known as ethylene/propylene/diene monomer (EPDM) and,in particular, ethylene/propylene/dicyclopentadiene terpolymers. Thepreferred rubber or elastomers are polybutadiene and SBR.

In one aspect, the rubber is preferably of at least two of diene-basedrubbers. For example, a combination of two or more rubbers is preferredsuch as cis 1,4-polyisoprene rubber (natural or synthetic, althoughnatural is preferred), 3,4-polyisoprene rubber,styrene/isoprene/butadiene rubber, emulsion and solution polymerizationderived styrene/butadiene rubbers, cis 1,4-polybutadiene rubbers andemulsion polymerization prepared butadiene/acrylonitrile copolymers.

In one aspect of this invention, an emulsion polymerization derivedstyrene/butadiene (E-SBR) might be used having a relatively conventionalstyrene content of about 20 to about 28 percent bound styrene or, forsome applications, an E-SBR having a medium to relatively high boundstyrene content; namely, a bound styrene content of about 30 to about 45percent.

The relatively high styrene content of about 30 to about 45 for theE-SBR can be considered beneficial for a purpose of enhancing traction,or skid resistance, of the tire tread. The presence of the E-SBR itselfis considered beneficial for a purpose of enhancing processability ofthe uncured elastomer composition mixture, especially in comparison to autilization of a solution polymerization prepared SBR (S-SBR).

By emulsion polymerization prepared E-SBR, it is meant that styrene and1,3-butadiene are copolymerized as an aqueous emulsion. Such are wellknown to those skilled in such art. The bound styrene content can vary,for example, from about 5 to about 50 percent. In one aspect, the E-SBRmay also contain acrylonitrile to form a terpolymer rubber, as E-SBAR,in amounts, for example, of about 2 to about 30 weight percent boundacrylonitrile in the terpolymer.

Emulsion polymerization prepared styrene/butadiene/acrylonitrilecopolymer rubbers containing about 2 to about 40 weight percent boundacrylonitrile in the copolymer are also contemplated as diene-basedrubbers for use in this invention.

The solution polymerization prepared SBR (S-SBR) typically has a boundstyrene content in a range of about 5 to about 50, preferably about 9 toabout 36, percent. The S-SBR can be conveniently prepared, for example,by organo lithium catalyzation in the presence of an organic hydrocarbonsolvent.

A purpose of using S-SBR is for improved tire rolling resistance as aresult of lower hysteresis when it is used in a tire tread composition.

The 3,4-polyisoprene rubber (3,4-PI) is considered beneficial for apurpose of enhancing the tire's traction when it is used in a tire treadcomposition. The 3,4-PI and use thereof is more fully described in U.S.Pat. No. 5,087,668 which is incorporated herein by reference. The Tgrefers to the glass transition temperature which can conveniently bedetermined by a differential scanning calorimeter at a heating rate of10° C. per minute.

The cis 1,4-polybutadiene rubber (BR) is considered to be beneficial fora purpose of enhancing the tire tread's wear, or treadwear. Such BR canbe prepared, for example, by organic solution polymerization of1,3-butadiene. The BR may be conveniently characterized, for example, byhaving at least a 90 percent cis 1,4-content.

The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber arewell known to those having skill in the rubber art.

The term "phr" as used herein and, according to conventional practice,refers to "parts by weight of a respective material per 100 parts byweight of rubber, or elastomer."

The bis anils used in the present invention are of the formula ##STR3##where R¹ and R² may be the same or different and are independentlyselected from alkyls having from 1 to 5 carbon atoms and X is selectedfrom the group consisting of H; OH; OAlk where Alk is an alkyl havingfrom 1 to 3 carbon atoms; COOH and; COO⁻ M⁺ where M is a metal selectedfrom the group consisting of Zn, Na, Ca and Mg; and y is 0 to 2.Preferably, each R¹ is an alkyl group having from 1 to 2 carbon atomsand X is COO⁻ M⁺ where M⁺ is Zn. When X is OAlk, preferably Alk is analkyl having from 1 to 2 carbon atoms.

Depending on the method of production, the bis anils may comprise a highpurity product or mixture of products. For example, it is contemplatedherein that not only high purity bis anils of the above Formula I may beused but also mixtures of bis anils of the above formula may be used,such as where some of the bis anils have different R¹ and/or Xsubstituents.

The bis anil compounds may be prepared by reacting a compound of theformula: ##STR4## where R¹, R² and y are defined above, with a compoundof the formula: ##STR5## where X is as defined above except in theinstance where the desired product is where X is COO⁻ M⁺. In thisinstance, one reacts aminobenzoic acid with the compound of Formula IIand then reacts its reaction product with the acetate of the desiredmetal; such as, zinc acetate, sodium acetate and the like.

Examples of suitable starting materials of Formula II include2,3-butanedione, 2,3 pentanedione, 2,4 pentanedione, 2,3-hexanedione,2,5-hexanedione, 3,4-hexanedione and the like.

Example of suitable starting materials of Formula III include aniline,aminophenol, aminobenzoic acid, ethoxyaniline, methoxyaniline,propoxyaniline and isopropoxyaniline.

The mole ratio of the compound of Formula II to the compound of FormulaIII may vary from 0.5:2 to 2:0.5. Preferably, the mole ratio ranges from1:2 to 2:2:5.

An organic solvent may be used to dissolve the acid of Formula II toincrease heat transfer and to facilitate water removal through a refluxtrap. The solvent is preferably inert to the reaction. Illustrative ofsolvents suitable for use in the practice of this invention include:saturated and aromatic hydrocarbons; e.g., hexane, octane, dodecane,naphtha, decalin, tetrahydronaphthalene, kerosene, mineral oil,cyclohexane, cycloheptane, alkyl cycloalkane, benzene, toluene, xylene,alkyl-naphthalene, and the like; alcohols such as methanol, ethanol,propanol; ethers such as tetrahydrofuran, tetrahydropyran, diethylether,1,2-dimethoxybenzene, 1,2-diethoxybenzene, the mono and dialkylethers ofethylene glycol, propylene glycol, butylene glycol, diethylene glycol,dipropylene glycol, oxyethyleneoxypropylene glycol, and the like;fluorinated hydrocarbons that are inert under the reaction conditionssuch as perfluoroethane, monofluorobenzene, and the like. Another classof solvents are sulfones such as dimethylsulfone, diethylsulfone,diphenolsulfone, sulfolane, and the like. Mixtures of the aforementionedsolvents may be employed so long as they are compatible with each otherunder the conditions of the reaction are anhydrous and not interferewith the reaction.

The reaction may be conducted over a variety of temperature ranges. Thetemperatures may range from moderate to an elevated temperature. Ingeneral, the imine-forming reaction may be conducted at a temperatureranging from about 18° C. to about 150° C. The preferred temperaturerange is from about 64° C. to about 100° C., while the most preferredtemperature range is from about 64° C. to about 78° C.

The reaction may be conducted over a variety of pressures. Preferably,the reaction is conducted at a pressure range of from about 0 to about100 psig.

The reaction is conducted for a period of time sufficient to produce thedesired bis anil compound of Formula I. In general, the reaction timecan vary from minutes to several hours. If the more sluggish reactionconditions are selected, then the reaction time will have to be extendeduntil the desired product is produced. It is appreciated that theresidence time of the reactants will be influenced by the reactiontemperature, concentration and choice of catalyst, if any, reactionpressure, concentration and choice of solvent, and other factors such asthe use of microwaves.

The reaction may be carried out in a batch, semi-continuous orcontinuous manner. The imine-forming reaction may be conducted in asingle reaction zone or in a plurality of reaction zones, in series orin parallel. The reaction may be conducted intermittently orcontinuously. The reaction may be conducted in a vessel equipped with athermometer, stirrer and a distillation column to separate water thatdistills from reactants and optionally a Dean Stark trap or an anhydroussolvent such as anhydrous alcohol may be used and the generated water issimply pulled from the imine-forming reaction. The reactor may be fittedwith internal and/or external heat exchangers to control temperaturefluctuations. Preferably, an agitation means is available to ensure auniform reaction. Mixing induced by vibration, shaker, stirrer,rotating, oscillation, etc, are all illustrative of the types ofagitation means which are contemplated for use in the anil-formingreaction. Such agitation means are available and well known to thoseskilled in the art.

The bis anils used in the present invention may be added to the rubberby any conventional technique such as on a mill or in a Banbury. Theamount of bis anils may vary widely depending on the type of rubber andother compounds present in the vulcanizable composition. Generally, theamount of bis anil compound is used in a range of from about 0.05 toabout 10.0 phr with a range of 0.1 to about 5.0 phr being preferred. Thebis anil compound is preferably added in the nonproductive stage.

For ease in handling, the bis anil compound may be used per se or may bedeposited on suitable carriers. Examples of carriers which may be usedin the present invention include silica, carbon black, alumina,kieselguhr, silica gel and calcium silicate.

The rubber composition may contain a sufficient amount of filler tocontribute a reasonably high modulus and high resistance to tear. Thetotal filler may be added in amounts ranging from 10 to 250 phr. Whenthe filler includes silica, the silica is present in an amount rangingfrom 5 to 80 phr. Preferably, the amount of silica ranges from 5 to 50phr. When the filler is carbon black, the amount of carbon black mayvary. Generally speaking, the amount of carbon black, when used, willvary from 1 to 80 phr. Preferably, the amount of carbon black will rangefrom 1 to 40 phr. It is to be appreciated that a silica coupler may beused in conjunction with a carbon black, namely pre-mixed with a carbonblack prior to addition to the rubber composition, and such carbon blackis to be included in the aforesaid amount of carbon black for the rubbercomposition formulation.

The commonly employed siliceous pigments used in rubber compoundingapplications can be used as the silica in this invention, includingpyrogenic and precipitated siliceous pigments (silica), althoughprecipitate silicas are preferred. The siliceous pigments preferablyemployed in this invention are precipitated silicas such as, forexample, those obtained by the acidification of a soluble silicate;e.g., sodium silicate.

Such silicas might be characterized, for example, by having a BETsurface area, as measured using nitrogen gas, preferably in the range ofabout 40 to about 600, and more usually in a range of about 50 to about300 square meters per gram. The BET method of measuring surface area isdescribed in the Journal of the American Chemical Society, Volume 60,page 304 (1930).

The silica may also be typically characterized by having adibutylphthalate (DBP) absorption value in a range of about 100 to about400, and more usually about 150 to about 300.

The silica might be expected to have an average ultimate particle size,for example, in the range of 0.01 to 0.05 micron as determined by theelectron microscope, although the silica particles may be even smaller,or possibly larger, in size.

Various commercially available silicas may be considered for use in thisinvention such as, only for example herein, and without limitation,silicas commercially available from PPG Industries under the Hi-Siltrademark with designations 210, 243, etc; silicas available fromRhone-Poulenc, with, for example, designations of Z1165MP and Z165GR andsilicas available from Degussa AG with, for example, designations VN2and VN3, etc.

The bis anil compound may be added to a rubber compound which alsocontains a sulfur containing organosilicon compound. Examples ofsuitable sulfur containing organosilicon compounds are of the formula:

    Z--Alk--S.sub.n --Alk--Z

in which Z is selected from the group consisting of ##STR6## where R² isan alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl;

R³ is alkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8 carbonatoms;

Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is aninteger of 2 to 8.

Specific examples of sulfur containing organosilicon compounds which maybe used in accordance with the present invention include:3,3'-bis(trimethoxysilylpropyl) disulfide,3,3'-bis(triethoxysilylpropyl) tetrasulfide,3,3'-bis(triethoxysilylpropyl) octasulfide,3,3'-bis(trimethoxysilylpropyl) tetrasulfide,2,2'-bis(triethoxysilylethyl) tetrasulfide,3,3'-bis(trimethoxysilylpropyl) trisulfide,3,3'-bis(triethoxysilylpropyl) trisulfide,3,3'-bis(tributoxysilylpropyl) disulfide,3,3'-bis(trimethoxysilylpropyl) hexasulfide,3,3'-bis(trimethoxysilylpropyl) octasulfide,3,3'-bis(trioctoxysilylpropyl) tetrasulfide,3,3'-bis(trihexoxysilylpropyl) disulfide,3,3'-bis(tri-2"-ethylhexoxysilylpropyl) trisulfide,3,3'-bis(triisooctoxysilylpropyl) tetrasulfide,3,3'-bis(tri-t-butoxysilylpropyl) disulfide, 2,2'-bis(methoxy diethoxysilyl ethyl) tetrasulfide, 2,2'-bis(tripropoxysilylethyl) pentasulfide,3,3'-bis(tricyclohexoxysilylpropyl) tetrasulfide,3,3'-bis(tricyclopentoxysilylpropyl) trisulfide,2,2'-bis(tri-2"-methylcyclohexoxysilylethyl) tetrasulfide,bis(trimethoxysilylmethyl) tetrasulfide, 3-methoxy ethoxy propoxysilyl3'-diethoxybutoxy-silylpropyltetrasulfide, 2,2'-bis(dimethylmethoxysilylethyl) disulfide, 2,2'-bis(dimethyl sec.butoxysilylethyl)trisulfide, 3,3'-bis(methyl is butylethoxysilylpropyl) tetrasulfide,3,3'-bis(di t-butylmethoxysilylpropyl) tetrasulfide, 2,2'-bis(phenylmethyl methoxysilylethyl) trisulfide, 3,3'-bis(diphenylisopropoxysilylpropyl) tetrasulfide, 3,3'-bis(diphenylcyclohexoxysilylpropyl) disulfide, 3,3'-bis(dimethylethylmercaptosilylpropyl) tetrasulfide, 2,2'-bis(methyldimethoxysilylethyl) trisulfide, 2,2'-bis(methylethoxypropoxysilylethyl) tetrasulfide, 3,3'-bis(diethylmethoxysilylpropyl) tetrasulfide, 3,3'-bis(ethyl di-sec.butoxysilylpropyl) disulfide, 3,3'-bis(propyl diethoxysilylpropyl)disulfide, 3,3'-bis(butyl dimethoxysilylpropyl) trisulfide,3,3'-bis(phenyl dimethoxysilylpropyl) tetrasulfide, 3-phenylethoxybutoxysilyl 3'-trimethoxysilylpropyl tetrasulfide,4,4'-bis(trimethoxysilylbutyl) tetrasulfide,6,6'-bis(triethoxysilylhexyl) tetrasulfide,12,12'-bis(triisopropoxysilyl dodecyl) disulfide,18,18'-bis(trimethoxysilyloctadecyl) tetrasulfide,18,18'-bis(tripropoxysilyloctadecenyl) tetrasulfide,4,4'-bis(trimethoxysilyl-buten-2-yl) tetrasulfide,4,4'-bis(trimethoxysilylcyclohexylene) tetrasulfide,5,5'-bis(dimethoxymethylsilylpentyl) trisulfide,3,3'-bis(trimethoxysilyl-2-methylpropyl) tetrasulfide,3,3'-bis(dimethoxyphenylsilyl-2-methylpropyl) disulfide.

The preferred sulfur containing organosilicon compounds are the3,3'-bis(trimethoxy or triethoxy silylpropyl) sulfides. The mostpreferred compound is 3,3'-bis(triethoxysilylpropyl) tetrasulfide.Therefore as to the above formula, preferably Z is ##STR7## where R³ isan alkoxy of 2 to 4 carbon atoms, with 2 carbon atoms being particularlypreferred; Alk is a divalent hydrocarbon of 2 to 4 carbon atoms with 3carbon atoms being particularly preferred; and n is an integer of from 3to 5 with 4 being particularly preferred.

The amount of the sulfur containing organosilicon compound of the aboveformula in a rubber composition will vary depending on the level ofsilica that is used. Generally speaking, the amount of the sulfurcontaining organosilicon, compound of, if used, will range from 0.01 to1.0 parts by weight per part by weight of the silica. Preferably, theamount will range from 0.05 to 0.4 parts by weight per part by weight ofthe silica.

It is readily understood by those having skill in the art that therubber composition would be compounded by methods generally known in therubber compounding art, such as mixing the various sulfur-vulcanizableconstituent rubbers with various commonly used additive materials suchas, for example, sulfur donors, curing aids, such as activators andretarders and processing additives, such as oils, resins includingtackifying resins and plasticizers, fillers, pigments, fatty acid, zincoxide, waxes, antioxidants and antiozonants and peptizing agents. Asknown to those skilled in the art, depending on the intended use of thesulfur vulcanizable and sulfur-vulcanized material (rubbers), theadditives mentioned above are selected and commonly used in conventionalamounts. Typical amounts of reinforcing-type carbon blacks(s), for thisinvention, if used, are herein set forth. Representative examples ofsulfur donors include elemental sulfur (free sulfur), an aminedisulfide, polymeric polysulfide and sulfur olefin adducts. Preferably,the sulfur vulcanizing agent is elemental sulfur. The sulfur vulcanizingagent may be used in an amount ranging from 0.5 to 8 phr, with a rangeof from 1.5 to 6 phr being preferred. Typical amounts of tackifierresins, if used, comprise about 0.5 to about 10 phr, usually about 1 toabout 5 phr. Typical amounts of processing aids comprise about 1 toabout 50 phr. Such processing aids can include, for example, aromatic,napthenic and/or paraffinic processing oils. Typical amounts ofantioxidants comprise about 1 to about 5 phr. Representativeantioxidants may be, for example, diphenyl-p-phenylenediamine andothers, such as, for example, those disclosed in the Vanderbilt RubberHandbook (1978), pages 344-346. Typical amounts of antiozonants compriseabout 1 to 5 phr. Typical amounts of fatty acids, if used, which caninclude stearic acid comprise about 0.5 to about 3 phr. Typical amountsof zinc oxide comprise about 2 to about 5 phr. Typical amounts of waxescomprise about 1 to about 5 phr. Often microcrystalline waxes are used.Typical amounts of peptizers comprise about 0.1 to about 1 phr. Typicalpeptizers may be, for example, pentachlorothiophenol anddibenzamidodiphenyl disulfide.

In one aspect of the present invention, the rubber compositioncontaining the bis anil compound of Formula I is sulfur-cured orvulcanized.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system may be used; i.e., primaryaccelerator. The primary accelerator(s) may be used in total amountsranging from about 0.5 to about 4, preferably about 0.8 to about 1.5,phr. In another embodiment, combinations of a primary and a secondaryaccelerator might be used with the secondary accelerator being used insmaller amounts, such as from about 0.05 to about 3 phr, in order toactivate and to improve the properties of the vulcanizate. Combinationsof these accelerators might be expected to produce a synergistic effecton the final properties and are somewhat better than those produced byuse of either accelerator alone. In addition, delayed actionaccelerators may be used which are not affected by normal processingtemperatures but produce a satisfactory cure at ordinary vulcanizationtemperatures. Vulcanization retarders might also be used. Suitable typesof accelerators that may be used in the present invention are amines,disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides,dithiocarbamates and xanthates. Preferably, the primary accelerator is asulfenamide. If a second accelerator is used, the secondary acceleratoris preferably a guanidine, dithiocarbamate or thiuram compound.

The rubber compositions of the present invention may contain a methylenedonor and a methylene acceptor. The term "methylene donor" is intendedto mean a compound capable of reacting with a methylene acceptor (suchas resorcinol or its equivalent containing a present hydroxyl group) andgenerate the resin in-situ. Examples of methylene donors which aresuitable for use in the present invention includehexamethylenetetramine, hexaethoxymethylmelamine,hexamethoxymethylmelamine, lauryloxymethylpyridinium chloride,ethoxymethylpyridinium chloride, trioxan hexamethoxymethylmelamine, thehydroxy groups of which may be esterified or partly esterified, andpolymers of formaldehyde such as paraformaldehyde. In addition, themethylene donors may be N-substituted oxymethylmelamines, of the generalformula: ##STR8## wherein X is an alkyl having from 1 to 8 carbon atoms,R⁴, R⁵, R⁶, R⁷ and R⁸ are individually selected from the groupconsisting of hydrogen, an alkyl having from 1 to 8 carbon atoms and thegroup --CH₂ OX. Specific methylene donors includehexakis-(methoxymethyl)melamine,N,N',N"-trimethyl/N,N',N"-trimethylolmelamine, hexamethylolmelamine,N,N',N"-dimethylolmelamine, N-methylolmelamine, N,N'-dimethylolmelamine,N,N',N"-tris(methoxymethyl)melamine andN,N'N"-tributyl-N,N',N"-trimethylol-melamine. The N-methylol derivativesof melamine are prepared by known methods.

The amount of methylene donor and methylene acceptor that is present inthe rubber stock may vary. Typically, the amount of methylene donor andmethylene acceptor that each is present will range from about 0.1 phr to10.0 phr. Preferably, the amount of methylene donor and methyleneacceptor that each is present ranges from about 2.0 phr to 5.0 phr.

The weight ratio of methylene donor to the methylene acceptor may vary.Generally speaking, the weight ratio will range from about 1:10 to about10:1. Preferably, the weight ratio ranges from about 1:3 to 3:1.

The mixing of the rubber composition can be accomplished by methodsknown to those having skill in the rubber mixing art. For example, theingredients are typically mixed in at least two stages; namely, at leastone non-productive stage followed by a productive mix stage. The finalcuratives including sulfur vulcanizing agents are typically mixed in thefinal stage which is conventionally called the "productive" mix stage inwhich the mixing typically occurs at a temperature, or ultimatetemperature, lower than the mix temperature(s) than the precedingnon-productive mix stage(s). The rubber, fillers and bis anil compoundare mixed in one or more non-productive mix stages. The terms"non-productive" and "productive" mix stages are well known to thosehaving skill in the rubber mixing art.

When the rubber compound contains a bis anil compound, silica, as wellas a sulfur-containing organosilicon compound, if used, the rubbercompound may be subjected to a thermomechanical mixing step. Thethermomechanical mixing step generally comprises a mechanical working ina mixer or extruder for a period of time suitable in order to produce arubber temperature between 140° C. and 190° C. The appropriate durationof the thermomechanical working varies as a function of the operatingconditions and the volume and nature of the components. For example, thethermomechanical working may be from 1 to 20 minutes.

Vulcanization of the rubber composition of the present invention isgenerally carried out at conventional temperatures ranging from about100° C. to 200° C. Preferably, the vulcanization is conducted attemperatures ranging from about 110° C. to 180° C. Any of the usualvulcanization processes may be used such as heating in a press or mold,heating with superheated steam or hot air or in a salt bath.

Upon vulcanization of the sulfur-vulcanized composition, the rubbercomposition of this invention can be used for various purposes. Forexample, the sulfur-vulcanized rubber composition may be in the form ofa tire, belt or hose. In case of a tire, it can be used for various tirecomponents. Such tires can be built, shaped, molded and cured by variousmethods which are known and will be readily apparent to those havingskill in such art. Preferably, the rubber composition is used in thetread of a tire. As can be appreciated, the tire may be a passengertire, aircraft tire, truck tire and the like. Preferably, the tire is apassenger tire. The tire may also be a radial or bias, with a radialtire being preferred.

The invention may be better understood by reference to the followingexamples in which the parts and percentages are by weight unlessotherwise indicated.

The following examples are presented in order to illustrate but notlimit the present invention.

Cure properties were determined using a Monsanto oscillating discrheometer which was operated at a temperature of 150° C. and at afrequency of 11 hertz. A description of oscillating disc rheometers canbe found in the Vanderbilt Rubber Handbook edited by Robert O. Ohm(Norwalk, Conn., R. T. Vanderbilt Company, Inc., 1990), pages 554-557.The use of this cure meter and standardized values read from the curveare specified in ASTM D-2084. A typical cure curve obtained on anoscillating disc rheometer is shown on page 555 of the 1990 edition ofthe Vanderbilt Rubber Handbook.

In such an oscillating disc rheometer, compounded rubber samples aresubjected to an oscillating shearing action of constant amplitude. Thetorque of the oscillating disc embedded in the stock that is beingtested that is required to oscillate the rotor at the vulcanizationtemperature is measured. The values obtained using this cure test arevery significant since changes in the rubber or the compounding recipeare very readily detected. It is obvious that it is normallyadvantageous to have a fast cure rate.

The invention may be better understood by reference to the followingexamples in which the parts and percentages are by weight unlessotherwise indicated.

EXAMPLE 1 Preparation of Biacetyl-bis-hydroxyanil

A 2-liter flask was charged with 3-aminophenol (109 g, 1.0 mole) and 700ml of anhydrous methanol, followed by 46.2 g (0.5 mole) of2,3-butanedione (biacetyl) and refluxed for 8 hours and cooled. Thesolvent was distilled off at reduced pressure (29 inches of Hg vacuum)at 50° C. to yield 143 g of brown shiny crystals melting at 80-85° C.The proposed structure was confirmed by its NMR spectrum (run inDMSO-d6). The infrared spectrum showed carbonyl and amine loss and anilformation.

EXAMPLE 2 Preparation of Biacetyl-bis-(4-Carboxyanil)

The Biacetyl bis anil compound was prepared by refluxing 137 gr (1.0mole) of anthranilic acid and 43 gr (0.5 mole) of 2,3-butanedione(biacetyl) in 700 ml of anhydrous methanol for 12 hours in a 2-literflask. After the reaction, the solvent was stripped under reducedpressure to give 162 gr of a brown solid melting at 82-92° C. Infraredanalysis showed formation of the bis anil functions and loss of theketo-functions and its structure confirmed by NMR analysis.

EXAMPLE 3 Preparation of the Zinc Salt of Biacetyl-bis-(4-carboxyanil)

The biacetyl-bis-(4-carboxyanil) of Example 2 was mixed with 91.4 gr(0.50 Mole) of zinc acetate in 500 ml of dry xylenes and refluxed over a3-hour period where about 200 ml of xylene-acetic acid were removedthrough a Dean-Stark trap. The remaining solvent was removed underreduced pressure to give 212 gr of a solid zinc salt melting at 120-132°C. and giving a zinc analysis of 13.4 percent.

EXAMPLE 4 Preparation of Biacetyl-bis-anil

Aniline (100 gr, 1.08 moles) and 700 ml of anhydrous methanol werecharged into a 2-liter flask, followed by 46.2 gr (0.54 mole) of2,3-butanedione (biacetyl) and refluxed for 6 hours and cooled overnightto give 37.9 gr of a tan solid precipitate melting at 135-140° C. andshowing an infrared spectrum of carbonyl loss and anil formation and itsstructure confirmed by NMR analysis.

EXAMPLE 5 Preparation of Biacetyl-bis-(4-ethoxyanil)

P-phenetidine (4-ethoxyaniline), 137 gr (1.0 mole) and 700 ml ofanhydrous methanol were charged into a 2-liter flask, followed by 43 gr(0.50 mole) of 2,3-butanedione and refluxed 8 hours to give 54 gr of asolid precipitate melting at 172-176° C. and showing bis anil formationby infrared spectroscopy and NMR analyses.

EXAMPLE 6

In this example, the use of the biacetyl-bis-(carboxyanil) of Example 2,the zinc biacetyl-bis-(carboxyanil) of Example 3 and thebiacetyl-bis-anil of Example 4 were evaluated in rubber. Rubbercompositions containing the materials set out in Tables 1 and 2 wereprepared in a BR Banbury™ mixer using three separate stages of addition(mixing), namely, two non-productive mix stages and one productive mixstage.

The rubber compositions are identified herein as Samples 1-6. Samples 1and 6 (Controls) contained no bis anil compound. Sample 2 contained 2phr of the biacetyl-bis-(carboxyanil) of Example 2. Sample 3 contained 2phr of the zinc biacetyl-bis-(carboxyanil) of Example 3. Sample 4contained 2 phr of the biacetyl-bis-anil of Example 4. Sample 5contained 2 phr of the biacetyl-bis-(ethoxyanil) of Example 5.

The samples were cured at about 135° C. for about 18 minutes.

Table 2 illustrates the behavior and physical properties of the curedsamples 1-6.

                  TABLE 1                                                         ______________________________________                                        Samples       1      2      3     4    5    6                                 ______________________________________                                        First Non-Productive                                                          Natural Rubber.sup.1                                                                        100.0  100.0  100.0 100.0                                                                              100.0                                                                              100.0                             Carbon Black.sup.2                                                                          40.0   40.0   40.0  40.0 40.0 40.0                              Stearic Acid  2.0    2.0    2.0   2.0  2.0  2.0                               Processing Oil                                                                              5.0    5.0    5.0   5.0  5.0  5.0                               Antidegradant.sup.3                                                                         1.0    1.0    1.0   1.0  1.0  1.0                               Antidegradant.sup.4                                                                         1.5    1.5    1.5   1.5  1.5  1.5                               Microcrystalline Wax                                                                        0.5    0.5    0.5   0.5  0.5  0.5                               Paraffinic Wax                                                                              0.5    0.5    0.5   0.5  0.5  0.5                               Second Non-Productive                                                         1st Non-Productive                                                                          150.5  150.5  150.5 150.5                                                                              150.5                                                                              150.5                             Silica.sup.5  25.0   25.0   25.0  25.0 25.0 25.0                              Organosilicon.sup.6                                                                         2.5    2.5    2.5   2.5  2.5  2.5                               Biacetyl-bis-(carboxyanil).sup.7                                                            0      2.0    0     0    0    0                                 Zn Salt of Biacetyl-bis-                                                                    0      0      2.0   0    0    0                                 (carboxyanil).sup.8                                                           Biacetyl-bis-anil.sup.9                                                                     0      0      0     2.0  0    0                                 Biacetyl-bis-(ethoxyanil).sup.10                                                            0      0      0     0    2.0  0                                 Productive                                                                    Second Non-Productive                                                                       178.0  178.0  178.0 178.0                                                                              178.0                                                                              178.0                             Perkaline 900.sup.11                                                                        1.2    1.2    1.2   1.2  1.2  1.2                               Zinc Oxide    5.0    5.0    5.0   5.0  5.0  5.0                               Sulfur        1.0    1.0    1.0   1.0  1.0  1.0                               Accelerator.sup.12                                                                          1.7    1.7    1.7   1.7  1.7  1.7                               ______________________________________                                         .sup.1 SMR5                                                                   .sup.2 N234                                                                   .sup.3 Polymerized trimethyldihydroquinoline                                  .sup.4 N1,3-dimethylbutyl-Nphenyl-p-phenylenediamine                          .sup.5 HiSil 243 supplied by PPG                                              .sup.6 Obtained as bis(3-triethoxysilylpropyl) tetrasulfide, which is         commercially available as X50S from Degussa Gmbh and is provided in a         50/50 by weight blend with carbon black.                                      .sup.7 Prepared in Example 2                                                  .sup.8 Prepared in Example 3                                                  .sup.9 Prepared in Example 4                                                  .sup.10 Prepared in Example 5                                                 .sup.11 N,Nm-xylylene bis citraconimide commercially available from           Flexys.                                                                       .sup.12 Nt-butyl-2-benzothiazole sulfenamide                             

                  TABLE 2                                                         ______________________________________                                        Samples       1      2      3     4    5    6                                 ______________________________________                                        Biacetyl-bis-(carboxyanil)                                                                  0      2.0    0     0    0    0                                 Zn Salt of Biacetyl-bis-                                                                    0      0      2.0   0    0    0                                 (carboxyanil)                                                                 Biacetyl-bis-anil                                                                           0      0      0     2.0  0    0                                 Biacetyl-bis-ethoxyanil                                                                     0      0      0     0    2.0  0                                 Rheometer, 135° C.                                                     Max Torque    41.0   45.0   47.0  42.0 41.8 41.8                              Min Torque    13.0   14.0   13.9  13.2 13.7 13.7                              Delta Torque  28.0   31.0   33.1  28.8 28.1 28.1                              T90 (min)     35.8   43.0   36.0  24.0 15.0 35.0                              T25 (min)     23.4   20.1   21.4  13.4 6.6  23.8                              Stress Strain 36' @ 150° C.                                            100% M (MPa)  2.6    3.0    3.2   2.5  2.6  2.6                               300% M (MPa)  14.5   15.6   16.8  13.9 13.5 14.5                              Tensile Strength (MPa)                                                                      22.8   23.1   23.2  23.1 22.6 22.5                              Elongation @ Break (%)                                                                      492    480    452   524  526  488                               Hardness, RT  67.7   71.6   72.7  69.4 69.7 69.1                              100C          61.1   64.5   65.6  62.0 62.2 62.2                              Rebound, RT   41.8   40.5   41.9  42.3 41.2 41.9                              100C          57.0   55.5   57.3  56.3 53.9 57.3                              DIN Abrasion (RT)                                                                           126    131    127   140  140  131                               Strebler Adhesion (120° C.)                                                          251.9  225.0  169.1 257.6                                                                              243.2                                                                              208.8                             ______________________________________                                    

Table 2 shows that the use biacetyl-bis(carboxyanil) will give increasedcure state over the control as shown by increased delta torque, 300percent modulus and hardness with comparable rebound. When the zinc saltof this diacid bis anil is run head to head, the state of cure (deltatorque, modulus and hardness) is further increased again with comparablerebound which represents a low heat buildup rubber.

The use of biacetyl-bis-anil accelerates the cure (lower T90) whilemaintaining the cured physical properties of the controls. Similarly,the use of biacetyl-bis-ethoxyanil accelerates the cure rate (T90) ofthe rubber while maintaining the state of cure (delta torque) of therubber compound, but the cure is appreciably faster (T90=15 minutes).The accelerated cure without scorchiness can substantially increaseproduction of cured rubber compounds per unit time. Also, this type ofcure accelerator that maintains the state of cure can be selectivelycompounded into portions of a heavy or thick tire to properly cureinternal components that effectively feel less cure equivalents than theouter compounds near the heated cure equipment.

EXAMPLE 7

In this Example, the use of the biacetyl-bis-(hydroxyanil) of Example 1was evaluated in rubber and, in particular, as a methylene acceptor.

Rubber compositions containing the materials set out in Tables 3 and 4were prepared in a BR Banbury™ mixer using three separate stages ofaddition (mixing); namely, two non-productive mix stages and oneproductive mix stage.

The rubber compositions are identified herein as Samples 1-3. Sample 1(control) contained no bis anil compound. Sample 2 contained 4 phr ofthe biacetyl-bis-(hydroxyanil) of Example 1 along with 4 phr ofhexamethoxymethyl melamine. Sample 3 contained nobiacetyl-bis-(hydroxyanil) but did contain 4 phr of resorcinol and 4 phrof hexamethoxymethyl melamine.

The samples were cured at about 150° C. for about 18 minutes.

Table 4 illustrates the behavior and physical properties of the curedsamples 1-3.

                  TABLE 3                                                         ______________________________________                                        Sample            1         2      3                                          ______________________________________                                        First Non-Productive                                                          E-SBR.sup.1       100.0     100.0  100.0                                      Carbon Black.sup.2                                                                              40.0      40.0   40.0                                       Silica.sup.3      25.0      25.0   25.0                                       Stearic Acid      2.0       2.0    2.0                                        Processing Oil    4.5       4.5    4.5                                        Antidegradant.sup.4                                                                             1.0       1.0    1.0                                        Antidegradant.sup.5                                                                             1.5       1.5    1.5                                        Microcrystalline Wax                                                                            0.5       0.5    0.5                                        Paraffinic Wax    0.5       0.5    0.5                                        Resorcinol        0         0      4.0                                        Second Non-Productive                                                         1st Non-Productive                                                                              175.0     175.0  179.0                                      Organosilicon.sup.6                                                                             2.5       2.5    2.5                                        Productive                                                                    2nd Non-Productive                                                                              177.5     177.5  181.5                                      Biacetyl-bis-(hydroxyanil).sup.7                                                                0         4.0    0                                          Hexamethoxymethyl melamine                                                                      0         4.0    4.0                                        Zinc Oxide        5.0       5.0    5.0                                        Sulfur            1.0       1.0    1.0                                        Accelerator.sup.8                                                             ______________________________________                                         .sup.1 Emulsion polymerized styrenebutadiene rubber which is commercially     available from The Goodyear Tire & Rubber Company as PLF 1502                 .sup.2 N234                                                                   .sup.3 HiSil 243 supplied by PPG                                              .sup.4 Polymerized trimethyldihydroquinoline                                  .sup.5 N1,3-dimethylbutyl-Nphenyl-p-phenylene diamine                         .sup.6 Obtained as bis(3-triethoxysilylpropyl) tetrasulfide, which is         commercially available as X50S from Degussa Gmbh and is provided in a         50/50 by weight blend with carbon black.                                      .sup.7 Prepared in Example 1                                                  .sup.8 Nt-butyl-2-benzothiazole sulfenamide                              

                  TABLE 4                                                         ______________________________________                                        Samples           1         2      3                                          ______________________________________                                        Biacetyl-bis-(hydroxyanil)                                                                      0         4      0                                          Resorcinol        0         0      4                                          Hexamethoxymethyl Melamine                                                                      0         4      4                                          Rheometer, 150° C.                                                     Max Torque        40.7      36.1   45.6                                       Min Torque        12.8      12.1   12.7                                       Delta Torque      27.9      24.0   32.9                                       T90               21.0      27.0   39.4                                       T25               9.3       9.1    9.8                                        Stress Strain 36' @ 150° C.                                            100% M (MPa)      2.5       2.2    2.6                                        300% M (MPa)      11.1      8.0    7.2                                        Tensile Strength (MPa)                                                                          21.5      16.9   13.4                                       Elongation @ Break (%)                                                                          557       602    564                                        Hardness, RT      69.1      70.7   79.8                                       100C              59.3      56.6   69.2                                       Rebound, RT       37.5      36.5   38.5                                       100C              49.4      41.9   40.6                                       Strebler Adhesion (120°)                                                                 127.3     59.8   51.0                                       ______________________________________                                    

Table 4 shows that comparable properties to the resorcinol control forresin formation are obtained when the bis anil is used as a methyleneacceptor.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

What is claimed is:
 1. A rubber composition comprising an elastomercontaining olefinic unsaturation and a bis anil compound of the formula##STR9## where R¹ and R² may be the same or different and areindependently selected from alkyls having from 1 to 5 carbon atoms and Xis selected from the group consisting of H; OH; OAlk where Alk is analkyl having from 1 to 3 carbon atoms; COOH and; COO⁻ M⁺ where M is ametal selected from the group consisting of Zn, Na, Ca and Mg; and y is0 to
 2. 2. The rubber composition of claim 1 wherein R¹ is an alkylhaving from 1 to 3 carbon atoms and X is COOH.
 3. The rubber compositionof claim 1 wherein X is COO⁻ M⁺ where M is Zn.
 4. The rubber compositionof claim 1 wherein X is H.
 5. The rubber composition of claim 1 whereinX is OH.
 6. The rubber composition of claim 1 wherein X is OAlk.
 7. Therubber composition of claim 6 wherein Alk is an alkyl having from 1 to 2carbon atoms.
 8. The rubber composition of claim 1 wherein X is COOH. 9.The composition of claim 1 wherein said bis anil is present in an amountranging from 0.05 to 10.0 phr.
 10. The composition of claim 1 wherein asulfur containing organosilicon compound is present and is of theformula:

    Z--Alk--S.sub.n --Alk--Z

in which Z is selected from the group consisting of ##STR10## where R²is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl; R³ isalkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8 carbon atoms;Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is aninteger of 2 to
 8. 11. The composition of claim 1 wherein a silicafiller is used in an amount ranging from 5 to 80 phr.
 12. Thecomposition of claim 11 wherein a sulfur containing organosiliconcompound is present in an amount ranging from 0.01 to 1.0 parts byweight per part by weight of said silica.
 13. The composition of claim 1wherein a carbon black is used in an amount ranging from 1 to 80 phr.14. The composition of claim 1 wherein said elastomer containingolefinic unsaturation is selected from the group consisting of naturalrubber, neoprene, polyisoprene, butyl rubber, polybutadiene,styrene-butadiene copolymer, styrene/isoprene/butadiene rubber, methylmethacrylate-butadiene copolymer, isoprene-styrene copolymer, methylmethacrylate-isoprene copolymer, acrylonitrile-isoprene copolymer,acrylonitrile-butadiene copolymer, EPDM and mixtures thereof.
 15. Thecomposition of claim 10 wherein said composition is thermomechanicallymixed at a rubber temperature in a range of from 140° C. to 190° C. fora total mixing time of from 1 to 20 minutes.
 16. A sulfur vulcanizedrubber composition which is prepared by heating the composition of claim1 to a temperature ranging from 100° C. to 200° C. in the presence of asulfur vulcanizing agent.
 17. The sulfur vulcanized rubber compositionof claim 16 in the form of a tire, belt or hose.
 18. A tire having atread comprised of the composition of claim 16.